The purpose of this research is to lower the death rate from gram-negative bacteremia by treating patients with antiserum against core glycolipid. We have already succeeded in lowering the death rate in patients from 26% to 14% by treating gram-negative bacteremia with antiserum against the J5 mutant and now propose to extend these studies to more patients in order to consolidate these results and establish their full significance. We also purpose to test the antiserum to core glycolipid for its prophylactic value in patients predisposed to lethal gram-negative infections, to increase its potency, and to explore the potential of active immunization with J5 vaccine.